Exploration Opportunities in the Northern Tarakan Basin - Based on Newly Acquired Seismic and Play Mapping
Jacques, John M.¹; Manur, Hendry²; Hoult, Ruth J.¹; Satyana, Awang H.³
¹Oil and Gas Consultancy, JMJ Petroleum, Singapore, Singapore.
²Star Energy Sentosa (Sebatik), Jakarta, Indonesia.
³BPMIGAS, Jakarta, Indonesia.
This paper highlights the results of a petroleum systems evaluation and opportunity screening of the northern part of the Tarakan Basin, Eastern Kalimantan. Based on newly acquired seismic, the tectonostratigraphic evolution of the basin has been reassessed, as a means of synthesising the basin's tectonic, structural and depositional history. This has been used to understand subsidence and uplift history for basin modelling purposes, with the aim to identify the timing of hydrocarbon generation and present day depths to expulsion thresholds for the key potential source intervals.
Five major NW-SE trending southeasterly plunging arches dominate the basin (Sebatik, Ahus, Bunyu, Tarakan and Latih), with a combination of structural and stratigraphic trapping along the axis of the up-dip sections of the arches accounting for virtually all production. A relatively simple hydrocarbon charge model is envisaged where migration from the source kitchen area(s) is focused up the plunging nose of each arch into proximal delta plain Plio-Pleistocene clastic reservoirs. The two largest fields in the basin, Tarakan and Bunyu, comprise faulted anticlinal structures.
Primarily developed in the Late Pleistocene, it has long been inferred that this structural trend of NW-SE arches continues into the northernmost part of the basin, with the possibility of the Sebatik and Ahus arches being structurally expressed on the islands of Sebatik and Nunukan, respectively. Recent field mapping, presented here, demonstrates the presence of a major SE plunging anticlinal fold in the centre of the Sebatik island (c.f. Tarakan and Bunyu islands); whereas, on the island of Nunukan, a broad open monoclinal fold dominates.
Basin modelling suggests late stage hydrocarbon migration from upper Mid Miocene Tabul Formation sources in the late Late Miocene to Late Pleistocene, with potential sources in the deeper section (e.g. lower Mid Miocene Meliat Formation and Lower Miocene Naintupo Formation) expelling in the Late Miocene (~8 Ma, Sembakung Graben). An understanding of the timing of oil and/or gas expulsion with regards to trap formation is therefore critical, together with the proximity of source with respect to migration distance.
The results of this exercise have been used to summarise proven plays and identify new play concepts as a predictive tool for the assessment of the hydrocarbon potential of the northern part of the basin, including the identification of offshore exploration targets.
AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012